Since you have nested classes, there is no shortcut to duplicate them at once. You can create new instance of the library class, but there's no way to create instance with all the added children inside. Think of duplication as simple instantiation of a class. It will be the same...

There are two ways to parse JSON in Flex. One is to use as3corelib. In that case, you need to change your code to var result:Object = com.adobe.serialization.json.JSON.decode(event.result) The other way (if you're targeting Flash Player 11+) is to use the built-in JSON class (in the default package): var result:Object...

It sounds like you're looking for getDefinitionByName(), which you could use to do something like this: import flash.utils.getDefinitionByName; private var LevelVectorClass:Class = getDefinitionByName("vector_land" + theLevel) as Class; private var land:Object = new LevelVectorClass(); ...